JP7169191B2 - acrylic rubber composition - Google Patents

Description

TECHNICAL FIELD The present invention relates to an acrylic rubber composition with improved tensile properties and heat resistance, and uses thereof.

In recent years, with the increasing demand for high performance and high functionality, attempts have been made to impart various properties by uniformly dispersing various fillers in polymers.

For example, in Patent Literature 1, by dispersing a small amount of boron nitride powder as a thermally conductive filler in a silicone rubber molding, high thermal conductivity is imparted while maintaining rubber flexibility.

Further, Patent Document 2 discloses a resin-sealed semiconductor device in which insulating properties are imparted by blending an inorganic filler into an epoxy resin.

Furthermore, Patent Document 3 discloses a nanocomposite in which physical properties such as breaking strength and bending fatigue resistance are improved by dispersing nano-sized fillers such as layered clay minerals in diene rubber.

Patent No. 3464752 Patent No. 5419948 Japanese Patent Application Laid-Open No. 2003-327751

On the other hand, acrylic rubber and its vulcanizates are excellent in physical properties such as heat aging resistance, oil resistance, mechanical properties, and compression set properties. It is widely used as a material for parts.

These members are also affected by the recent trend toward exhaust gas countermeasures and the increase in engine output, and there is a demand for materials that are superior in various physical properties such as tensile properties and heat resistance.

Accordingly, the main object of the present invention is to provide an acrylic rubber composition having sufficient tensile properties and heat resistance. Another object of the present invention is to provide a rubber cross-linked product obtained by cross-linking the above acrylic rubber composition.

As a result of extensive studies to solve the above problems, the present inventors have found that by finely dispersing layered clay minerals in acrylic rubber at nano-sizes, both tensile properties and heat resistance can be achieved, and these properties can be improved. can be sufficiently improved, leading to the completion of the present invention.

That is, the present invention provides an acrylic rubber composition containing 1 to 25 parts by mass of a layered clay mineral per 100 parts by mass of acrylic rubber, and a vulcanizate thereof.
Also, the acrylic rubber may be a copolymer of a (meth)acrylic acid alkyl ester and a crosslinking site monomer.
The crosslinking site monomer can contain at least one functional group selected from epoxy groups, carboxyl groups, and active chlorine groups. The cross-linking monomer may be included in an amount of 0.1-10% by weight based on the total weight of the acrylic rubber.
Also, the acrylic rubber may further contain an ethylene monomer. The ethylene monomer may be included in an amount of 0.1-10% by weight based on the total weight of the acrylic rubber.
Montmorillonite can be used as the layered clay mineral, and the montmorillonite can contain an onium salt.
The present invention also provides a vulcanizate obtained by vulcanizing the acrylic rubber composition, a rubber hose, a sealing part, and a vibration-proof rubber part manufactured using the vulcanizate.

According to the present invention, it is possible to provide an acrylic rubber composition excellent in both tensile properties and heat resistance. Furthermore, according to the present invention, it is also possible to provide a rubber cross-linked product obtained by cross-linking the above acrylic rubber composition.

Although the present invention will be described in detail below, the present invention is not limited to each embodiment shown below.

The acrylic rubber composition according to the present invention is characterized by dispersing layered clay minerals at the nano level. That is, the acrylic rubber composition of the present invention contains a layered clay mineral having nano-sized dimensions in a dispersed state.

The method for preparing the acrylic rubber composition in which the layered clay mineral is dispersed is not particularly limited. Obtained by kneading. As a rubber kneading device, rolls, kneaders, Banbury mixers, internal mixers, twin-screw extruders and the like can be used.

<Acrylic rubber>
The acrylic rubber used in the present invention is described below.
The acrylic rubber used in the present invention is obtained by copolymerizing a (meth)acrylic acid alkyl ester as a main component with a cross-linking site monomer. A "crosslinking site monomer" is a monomer having a functional group that forms a crosslinkage site (crosslinking point). Further, "mainly composed of (meth)acrylic acid alkyl ester" means that the total amount of monomer units derived from (meth)acrylic acid alkyl ester is 50% by mass or more with respect to the total mass of the acrylic rubber. means that For example, the content is preferably 75% to 99% by mass, more preferably 80% to 98% by mass, still more preferably 85% to 97% by mass, and even more preferably 90% to 96% by mass. The acrylic rubber used in the present invention may optionally be obtained by copolymerizing (meth)acrylic acid alkyl ester with vinyl acetate or the like. That is, vinyl acetate copolymerized acrylic rubber or ethylene-vinyl acetate copolymerized acrylic rubber may be used. The acrylic rubber used in the present invention is particularly preferably a copolymer of a (meth)acrylic acid alkyl ester, a crosslinking site monomer and an ethylene monomer.

The (meth)acrylic acid alkyl ester forms the skeleton of the acrylic rubber, and by selecting its type, the basic properties of the obtained acrylic rubber composition, such as normal physical properties, cold resistance, and oil resistance, can be adjusted. is. In the present invention, (meth)acrylic acid alkyl ester is synonymous with (meth)acrylate, and is a concept including both methacrylic acid alkyl ester (methacrylate) and acrylic acid alkyl ester (acrylate).

(Meth)acrylic acid alkyl esters are not particularly limited, but examples include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl ( meth)acrylate, n-pentyl (meth)acrylate, isoamyl (meth)acrylate, n-hexyl (meth)acrylate, 2-methylpentyl (meth)acrylate, n-octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate , n-decyl (meth)acrylate, n-dodecyl (meth)acrylate, n-octadecyl (meth)acrylate and the like (meth)acrylic acid alkyl esters. In addition, 2-methoxyethyl acrylate, 2-ethoxyethyl acrylate, 2-(n-propoxy)ethyl acrylate, 2-(n-butoxy)ethyl acrylate, 3-methoxypropyl acrylate, 3-ethoxypropyl acrylate, 2-(n -Propoxy)propyl acrylate, 2-(n-butoxy)propyl acrylate, 2-(2-ethoxyethoxy)ethyl acrylate and the like can also be used. The (meth)acrylic acid alkyl esters described above may be used alone, or two or more of them may be used in combination.

The acrylic rubber used in the present invention can preferably be one polymerized using ethyl acrylate and n-butyl acrylate as (meth)acrylic acid alkyl esters. That is, the acrylic rubber used in the present invention preferably contains ethyl acrylate monomer units and n-butyl acrylate monomer units, and more preferably contains these monomer units as main components. sell. That is, the acrylic rubber composition of the present invention contains ethyl acrylate monomers and n-butyl acrylate monomer units in total with respect to the total mass of the acrylic rubber, for example, preferably 75% by mass to 99% by mass, or more. The content is preferably 80% to 98% by mass, more preferably 85% to 97% by mass, and even more preferably 90% to 96% by mass.

For example, the acrylic rubber used in the present invention has an ethyl acrylate monomer unit content of, for example, 40% by mass to 60% by mass, preferably 42% by mass to 55% by mass, more preferably 44% by mass, based on the total mass of the acrylic rubber. % to 50% by mass, and the n-butyl acrylate monomer unit is, for example, 40% to 60% by mass, preferably 42% to 55% by mass, more preferably 44% by mass, based on the total mass of the acrylic rubber. % to 50% by mass. The content ratio of the monomer units is quantified based on the nuclear magnetic resonance spectrum obtained for the acrylic rubber or acrylic rubber composition.

By adjusting the blending amount of the unsaturated monomer described above, it is possible to adjust the cold resistance and oil resistance of the obtained acrylic rubber composition and its vulcanizate. For example, when ethyl acrylate and n-butyl acrylate are used to make acrylic rubber, cold resistance can be improved by increasing the copolymerization ratio of n-butyl acrylate, and by increasing the copolymerization ratio of ethyl acrylate. By doing so, the oil resistance can be improved.

The cross-linking monomer can be optionally copolymerized with a (meth)acrylic acid alkyl ester to promote intermolecular cross-linking and adjust the hardness and elongation properties of the resulting acrylic rubber. The cross-linking monomer must contain at least one of carboxyl group, epoxy group and active chlorine group as a functional group. That is, the acrylic rubber of the present invention can be an acrylic rubber containing at least one group selected from carboxyl groups, epoxy groups and active chlorine groups.

The cross-linking monomer is not particularly limited, but examples of cross-linking monomers containing a carboxyl group include acrylic acid, methacrylic acid, crotonic acid, 2-pentenoic acid, maleic acid, fumaric acid, itaconic acid, monoalkyl maleate, monoalkyl fumarate, monocyclohexyl maleate, monocyclohexyl fumarate, cinnamic acid and the like. Further, other cross-linkable monomers include, for example, those having an epoxy group such as glycidyl acrylate, glycidyl methacrylate, allyl glycidyl ether, methallyl glycidyl ether, 2-chloroethyl vinyl ether, 2-chloroethyl acrylate, vinylbenzyl Some have active chlorine groups such as chloride, vinyl chloroacetate and allyl chloroacetate. A single cross-linking monomer may be used, or multiple cross-linking monomers may be used in combination.

The cross-linking monomers used in the present invention are preferably maleic acid monoalkyl esters or fumaric acid monoalkyl esters. Although the number of carbon atoms in the monoalkyl group is not particularly limited, it can be, for example, preferably 1-8, more preferably 2-6, still more preferably 3-5. Monobutyl maleate, for example, can be used as the crosslinking site monomer. That is, a carboxyl group-containing acrylic rubber is preferably used as the acrylic rubber of the present invention. The carboxyl group is derived, for example, from the monoalkyl maleate or monoalkyl fumarate.

Alternatively, the cross-linking monomer used in the present invention can be glycidyl acrylate or glycidyl methacrylate. More preferred is glycidyl methacrylate. That is, an epoxy group-containing acrylic rubber is preferably used as the acrylic rubber of the present invention. The epoxy group is, for example, derived from the glycidyl acrylate or glycidyl methacrylate.

As described above, the acrylic rubber of the present invention is preferably a copolymer of, for example, a (meth)acrylic acid alkyl ester, a crosslinking site monomer and an ethylene monomer. Here, the content ratio of the monomer unit of the crosslinking site monomer is preferably 0.1% by mass to 10% by mass of the total mass of the acrylic rubber. More preferably 0.5% to 10% by mass, still more preferably 1% to 5% by mass, and even more preferably 1% to 4% by mass. If the content of the crosslinking site monomer is less than 0.1% by mass, the strength of the vulcanizate may be insufficient. If the content of the cross-linking monomer is more than 10% by mass, the vulcanizate may harden and lose its rubber elasticity.

When the cross-linking monomer has a carboxyl group, the amount of the monomer units is determined by dissolving raw rubber of the copolymer in toluene and performing neutralization titration using potassium hydroxide. When the cross-linking monomer has an epoxy group, the amount is measured by dissolving raw rubber of the copolymer in chloroform and titrating with a perchloric acid solution. When the cross-linkable monomer has an active chlorine group, the amount is measured by decomposition treatment by the oxygen flask combustion method and titration with silver nitrate.

In addition, the content ratio of the monomer unit of the crosslinking site monomer is the content ratio of the crosslinking site monomer containing the carboxyl group when only the one containing the carboxyl group is used as the crosslinking site monomer. When both an epoxy group-containing monomer and another cross-linking monomer are used, it is the total content of the epoxy group and the functional group derived from the other cross-linking monomer.

The acrylic rubber may be copolymerized with (meth)acrylic acid alkyl esters, crosslinking site monomers, or other monomers copolymerizable with vinyl acetate as long as the objects of the present invention are not impaired. Examples of other copolymerizable monomers include, but are not limited to, alkyl vinyl ketones such as vinyl acetate and methyl vinyl ketone, vinyl and allyl ethers such as vinyl ethyl ether and allyl methyl ether, styrene, α - Vinylaromatic compounds such as methylstyrene, chlorostyrene, vinyltoluene and vinylnaphthalene; vinylnitrile such as acrylonitrile and methacrylonitrile; Ethylenically unsaturated compounds such as vinylidene chloride, ethylene, and vinyl propionate.

The acrylic rubber used in the present invention is preferably polymerized with an ethylene monomer in addition to the (meth)acrylic acid alkyl ester and the crosslinking site monomer. By copolymerizing ethylene, an acrylic rubber with significantly improved strength can be obtained. The content of ethylene monomer units is preferably 0.1% by mass to 10% by mass, more preferably 0.5% by mass to 5% by mass, and still more preferably 1% by mass of the total mass of the acrylic rubber. ~3% by mass. If it is less than 0.1% by mass, the strength may be insufficient. If it is more than 10% by mass, the oil resistance may be remarkably deteriorated.
The content of ethylene monomer units is quantified based on the nuclear magnetic resonance spectrum obtained for the acrylic rubber or acrylic rubber composition.

In particular, when ethylene is copolymerized with acrylic rubber, for example, 100 parts by mass of acrylic rubber can be copolymerized with preferably 10 parts by mass or less of ethylene monomer. If it exceeds 10 parts by mass, the oil resistance may be remarkably deteriorated.

The acrylic rubber is obtained by copolymerizing the above monomers by known methods such as emulsion polymerization, suspension polymerization, solution polymerization and bulk polymerization. A method for producing acrylic rubber can be appropriately selected by those skilled in the art.

<Acrylic rubber composition>
The acrylic rubber composition according to the present invention will be described below.
As described above, the acrylic rubber composition according to the present invention contains the acrylic rubber and the layered clay mineral.

The layered clay mineral used in the present invention is not particularly limited, but examples thereof include smectite group clay minerals such as montmorillonite, hectorite and saponite. Among them, it is preferable to use montmorillonite.

Examples of the cation of the layered clay mineral include, but are not limited to, sodium salts, calcium salts, onium salts, and the like. Of these, onium salts are preferred. This cation suppresses the aggregation of the layered clay mineral and enables the layered clay mineral to be uniformly dispersed in the acrylic rubber composition at the nano level.

Onium salts are not particularly limited, but include quaternary ammonium salts and quaternary phosphonium salts. Examples of quaternary ammonium salts include tetramethylammonium chloride, tetrabutylammonium chloride, tetramethylammonium bromide, tetrabutylammonium bromide, decyltrimethylammonium chloride, bis(hydrogenated beef tallow)dimethylammonium chloride, etc., and quaternary phosphonium salts include tetraphenylphosphonium chloride, benzyltriphenylphosphonium chloride, tetraphenylphosphonium bromide, and methylphosphonium tetraphenylborate.

The content of the layered clay mineral is preferably 1 to 25 parts by mass, more preferably 4 to 25 parts by mass, still more preferably 8 to 20 parts by mass, and even more preferably 12 to 20 parts by mass in 100 parts by mass of the acrylic rubber. parts, most preferably 16-20 parts by weight. If the content is less than 1 part by mass, the effect of improving the strength may not appear. If it exceeds 25 parts by mass, the elongation may be remarkably deteriorated.

The acrylic rubber composition may further contain a vulcanizing agent or a vulcanization accelerator.

The vulcanizing agent is not particularly limited as long as it is commonly used for vulcanizing acrylic rubber compositions. A polyamine compound is suitable as the compound, and a vulcanization system containing a guanidine compound is particularly preferably used. Also, when a monomer having an epoxy group is used as the crosslinking site monomer, an imidazole compound is suitably used as the vulcanizing agent.

Examples of the polyamine compounds include 4,4′-bis(4-aminophenoxy)biphenyl, 4,4′-diaminodiphenyl sulfide, 1,3-bis(4-aminophenoxy)-2,2-dimethylpropane, 1, 3-bis(4-aminophenoxy)benzene, 1,4-bis(4-aminophenoxy)benzene, 1,4-bis(4-aminophenoxy)pentane, 2,2-bis[4-(4-aminophenoxy) ) phenyl]propane, 2,2-bis[4-(4-aminophenoxy)phenyl]sulfone, 4,4′-diaminodiphenylsulfone, bis(4-3-aminophenoxy)phenylsulfone, 2,2-bis [4-(4-aminophenoxy)phenyl]hexafluoropropane, 3,4′-diaminodiphenyl ether, 4,4′-diaminodiphenyl ether, 4,4′-diaminobenzanilide, bis[4-(4-aminophenoxy) Aromatic polyamine compounds such as phenyl]sulfone and 4,4'-bis(α,α-dimethylbenzyl)diphenylamine; hexamethylenediamine, hexamethylenediamine carbamate, N,N'-dicinnamylidene-1,6-hexanediamine, diethylenetriamine , triethylenetetramine, tetraethylenepentamine, and other aliphatic polyamine compounds.

Further, the guanidine compounds include guanidine, tetramethylguanidine, dibutylguanidine, diphenylguanidine, di-o-tolylguanidine and the like.

Further, the imidazole compounds include 1-methylimidazole, 1,2-dimethylimidazole, 1-methyl-2-ethylimidazole, 1-benzyl-2-methylimidazole, 1-benzyl-2-ethylimidazole, 1-benzyl -2-ethyl-5-methylimidazole, 1-benzyl-2-phenylimidazole, 1-benzyl-2-phenylimidazole trimellitate, 1-aminoethylimidazole, 1-aminoethyl-2-methylimidazole, 1 -aminoethyl-2-ethylimidazole, 1-cyanoethyl-2-methylimidazole, 1-cyanoethyl-2-phenylimidazole, 1-cyanoethyl-2-ethyl-4-methylimidazole, 1-cyanoethyl-2-undecyl imidazole, 1-cyanoethyl-2-methylimidazole trimellitate, 1-cyanoethyl-2-phenylimidazole trimellitate, 1-cyanoethyl-2-ethyl-4-methylimidazole trimellitate, 1-cyanoethyl-2-undecyl- Imidazole trimellitate, 2,4-diamino-6-[2′-methylimidazolyl-(1)′]ethyl-s-triazine isocyanuric acid adduct, 1-cyanoethyl-2-phenyl-4,5-di -(Cyanoethoxymethyl)imidazole, N-(2-methylimidazolyl-1-ethyl)urea, N,N'-bis-(2-methylimidazolyl-1-ethyl)urea, 1-(cyanoethylaminoethyl)-2 -methylimidazole, N,N'-[2-methylimidazolyl-(1)-ethyl]-aziboyldiamide, N,N'-[2-methylimidazolyl-(1)-ethyl]-dodecanedioyldiamide, N , N′-[2-methylimidazolyl-(1)-ethyl]-eicosandioyldiamide, 2,4-diamino-6-[2′-methylimidazolyl-(1)′]-ethyl-s-triazine, 2 , 4-diamino-6-[2′-undecylimidazolyl-(1)′]-ethyl-s-triazine, 1-dodecyl-2-methyl-3-benzylimidazolium chloride, 1,3-dibenzyl-2- and methylimidazolium chloride.

The content of the vulcanizing agent is not particularly limited, but is preferably 0.1 to 10 parts by mass, more preferably 0.3 to 5 parts by mass, based on 100 parts by mass of the acrylic rubber. By setting the content in this range, necessary and sufficient vulcanization treatment can be performed.

A vulcanization accelerator can be included to adjust the vulcanization rate. The vulcanization accelerator is not particularly limited, but specific examples include curing agents for epoxy resins, such as pyrolytic ammonium salts, organic acids, acid anhydrides, amines, sulfur, sulfur compounds, and the like. . The content of the vulcanization accelerator may be added within a range that does not impair the properties of the vulcanizate obtained from the acrylic rubber composition of the present invention.

The vulcanizate of the acrylic rubber composition of the present invention is obtained by kneading an acrylic rubber composition, a vulcanizing agent, a vulcanization accelerator and the like at a temperature below the vulcanization temperature. The acrylic rubber composition of the present invention can be molded into various desired shapes and then vulcanized to obtain a vulcanizate, or can be molded into various shapes after vulcanization. The vulcanization temperature can be appropriately set according to the compounding ratio of each component in the acrylic rubber composition and the type of vulcanizing agent. The time required for vulcanization is 1 to 10 hours, preferably 2 to 6 hours.

The apparatus for kneading, molding and vulcanizing the acrylic rubber composition and the apparatus for kneading and molding the vulcanized product of the acrylic rubber composition can be those commonly used in the rubber industry.

The acrylic rubber composition may be added with fillers, reinforcing agents, plasticizers, lubricants, anti-aging agents, stabilizers, silane coupling agents, and the like depending on the purpose for practical use.

As fillers and reinforcing agents, fillers and reinforcing agents that are commonly used for rubber applications can be added. Examples thereof include fillers and reinforcing agents such as carbon black, silica, talc, and calcium carbonate. The total amount of these additives to be added is preferably in the range of 20 to 100 parts by mass with respect to 100 parts by mass of the acrylic rubber composition.

As the plasticizer, a plasticizer that is commonly used for rubber applications can be added, and examples thereof include an ester plasticizer, a polyoxyethylene ether plasticizer, a trimellitate plasticizer, and the like. The amount of the plasticizer to be added is preferably in the range of up to about 50 parts by mass with respect to 100 parts by mass of the acrylic rubber composition.

The laminate and its vulcanizate of the present invention are particularly suitable for use as rubber hoses, sealing parts such as gaskets and packings, and anti-vibration rubber parts. That is, the present invention provides a rubber hose, sealing part, or anti-vibration rubber part containing the vulcanizate of the present invention. The rubber hose, sealing parts, and anti-vibration rubber parts may consist of the acrylic rubber composition of the present invention alone or its vulcanizate alone, or may be combined with other parts.

Examples of rubber hoses include transmission oil cooler hoses for automobiles, construction machinery, hydraulic equipment, engine oil cooler hoses, air duct hoses, turbo intercooler hoses, hot air hoses, radiator hoses, power steering hoses, fuel system hoses, and drain systems. hoses, etc.

As for the structure of the rubber hose, a reinforcing thread or wire may be provided in the middle of the hose or in the outermost layer of the rubber hose, as is commonly practiced.

Seal parts include, for example, engine head cover gaskets, oil pan gaskets, oil seals, lip seal packings, O-rings, transmission seal gaskets, crankshafts, camshaft seal gaskets, valve stems, power steering seal belt cover seals, constant velocity There are boot materials for joints and rack and pinion boot materials.

Anti-vibration rubber parts include, for example, damper pulleys, center support cushions, and suspension bushes.

EXAMPLES The present invention will be described in more detail with examples below, but the present invention is not limited to these examples.

Acrylic rubbers A and B were produced under the conditions shown below.
<Acrylic rubber A>
5.6 kg of ethyl acrylate, 5.6 kg of n-butyl acrylate, 560 g of monobutyl maleate, 17 kg of an aqueous solution of 4% by mass of partially saponified polyvinyl alcohol, and 22 g of sodium acetate were put into a pressure-resistant reaction vessel having an inner volume of 40 liters. , well mixed in advance with a stirrer to prepare a uniform suspension. After replacing the air in the upper part of the tank with nitrogen, ethylene was pressurized into the upper part of the tank to adjust the pressure to 3.5 MPa. Stirring was continued to maintain the inside of the tank at 55° C., and then an aqueous t-butyl hydroperoxide solution (0.25% by mass, 2 liters) was separately injected from an injection port to initiate polymerization. The temperature in the tank was kept at 55° C. during the reaction, and the reaction was completed in 6 hours. An aqueous sodium borate solution (3.5% by mass, 7 liters) was added to the resulting polymerization solution to solidify the polymer, which was then dehydrated and dried to obtain an acrylic rubber A.

The copolymer composition of this acrylic rubber A is 2.0% by mass of ethylene monomer units, 3.5% by mass of monobutyl maleate monomer units, 47.5% by mass of ethyl acrylate monomer units, n-butyl The acrylate monomer unit content was 47.0% by mass. Monobutyl maleate monomer units were quantified by dissolving raw rubber copolymer in toluene and performing neutralization titration using potassium hydroxide. For other copolymer compositions, nuclear magnetic resonance spectra were collected and each component was quantified.

<Acrylic rubber B>
Polymerization was initiated in the same manner as for Acrylic Rubber A, except that 150 g of glycidyl methacrylate was used in place of monobutyl maleate to obtain Acrylic Rubber B.

The copolymer composition of this acrylic rubber B is 2.0% by mass of ethylene monomer units, 3.5% by mass of glycidyl methacrylate monomer units, 47.5% by mass of ethyl acrylate monomer units, and n-butyl acrylate. The monomer unit content was 47.0% by mass. The amount of glycidyl methacrylate monomer was determined by dissolving raw rubber copolymer in chloroform and titrating with a perchloric acid solution. For other copolymer compositions, nuclear magnetic resonance spectra were collected and each component was quantified.

<Production of acrylic rubber composition>
The acrylic rubber obtained by the above method was kneaded with a 6-inch open roll according to the formulation shown in Table 1, and after being extruded into a sheet with a thickness of 2.4 mm, it was cured with a press vulcanizer at 170 ° C. for 50 minutes. Press vulcanization was performed.

The compounded reagents used in Table 1 are as follows.
・ Stearic acid: Lunax S-90 manufactured by Kao Corporation
・ Stearylamine: Farmin 80 manufactured by Kao Corporation
・ Liquid paraffin: Hicol K-230 manufactured by Kaneda Corporation
・ Anti-aging agent: Uniroyal Naugard 445 (4,4'-bis(α,α-dimethylbenzyl)diphenylamine)
・KA-4: 2,2-[bis-4-(4-aminophenoxy)phenyl]propane manufactured by Wakayama Seika Co., Ltd. ・XLA-60: Vulcanization accelerator manufactured by LANXESS ・Montmorillonite (Na salt): Southern clay ・Products Cloisite-Na+
・ Montmorillonite (Ca salt): Cloisite-Ca++ manufactured by Southern Clay Products
・ Montmorillonite (onium salt): Cloisite-30B manufactured by Southern Clay Products
The onium salt of montmorillonite is bis(hydrogenated beef tallow)dimethylammonium cation.

<Physical property test method>
The obtained acrylic rubber composition was evaluated for tensile strength, elongation at break, and heat resistance under the following conditions.
(1) Tensile strength/elongation at break Measured according to ASTM D 412-98.
(2) Heat resistance test Using a thermogravimetric measuring device, about 10 mg of a sample is heated to 600 ° C. at a temperature increase rate of 20 ° C./min in a nitrogen atmosphere (nitrogen flow rate of 35 ml / min), and the sample weight is 5%. The reduced temperature was measured as the decomposition temperature.
Table 1 shows the measurement results for each example and comparative example.

As is clear from Table 1, the acrylic rubber compositions of Examples 1 to 12 obtained by adding montmorillonite were found to be excellent in tensile properties, mechanical strength and heat resistance. Moreover, it was found that when the content of montmorillonite was more than 20 parts, the tensile properties were greatly deteriorated.

On the other hand, Comparative Example 1 has the same composition as Example 1 except that it does not contain montmorillonite. The result was that the weight loss temperature was also low.

As shown by comparison between Examples and Comparative Examples, the acrylic rubber composition of the present invention has excellent rubber physical properties, particularly excellent tensile properties and heat resistance.

Claims (11)

1 to 25 parts by mass of a layered clay mineral per 100 parts by mass of acrylic rubber containing ethylene monomer units ,
The layered clay mineral is montmorillonite containing an onium salt,
The onium salt is a quaternary ammonium salt or a quaternary phosphonium salt,
Acrylic rubber composition. 2. The acrylic rubber composition according to claim 1, wherein the acrylic rubber is a copolymer of a (meth)acrylic acid alkyl ester , a crosslinking site monomer and ethylene . 3. The acrylic rubber composition according to claim 2, wherein said crosslinking site monomer contains at least one functional group selected from an epoxy group, a carboxyl group and an active chlorine group. 4. The acrylic rubber composition according to claim 2, wherein the content of monomer units of said crosslinking site monomer is 0.1 to 10% by mass of the total mass of said acrylic rubber. The acrylic rubber composition according to any one of claims 1 to 4 , wherein the content of the ethylene monomer units is 0.1 to 10 mass% of the total mass of the acrylic rubber. The acrylic rubber composition according to any one of claims 1 to 5, further comprising a vulcanizing agent. The acrylic rubber composition according to any one of claims 1 to 6, which is an acrylic rubber composition that is vulcanized by heating. A vulcanizate obtained by vulcanizing the acrylic rubber composition according to any one of claims 1 to 7 . A rubber hose comprising the vulcanizate according to claim 8 . A sealing component comprising the vulcanizate of claim 8 . A vibration isolating rubber part containing the vulcanizate according to claim 8 .